Skid rail structure for forge furnaces



SePf- 15, 1953 J. D. NEsBlTT 2,652,240 'l SKID RAIL STRUCTURE FOR FORGE FURNACES Filed Nov. 20, 1950 o e o/e 2 Sheets-Sheet 1 INVENTOR.

JQ/yesbl/W www Sept- 15, 1953 J. D. NEsBn-T 2,652,240

l SKID RAIL STRUCTURE FOR FORGE FURNACES Filed NOV. 20, 1950 2 Sheets-Sheet 2 `56 INVENTOR. y :JEL .El 4a *l +v 71 QA/65h77 Patented Sept. 15, 1953 UNITED STATES PATENT ori-ICE SIUD RAIL STRUCTURE FOR FORGE FURNACES John D. Nesbitt, Sylvania, Ohio, assignor to Sur-` face Combustion Corporation, Toledo, Ohio, a corporation of Ohio Application November 20, 1950, Serial No. 196,582 1 Claim. (Cl. 263--6)l This inventionrelates to a fuel heated forge outlet pipe at` 46. The charging end of the furfurnace for use in plants where work pieces are nace is at the left. as viewed in Fig. 'l and the shaped between forging dies, as in hammer, work pieces are fed into the furnace by a reciproprovide improvements in skid rail structures for 5 pieces are placed by hand or otherwise. The a; fast heating furnace which will heat work` heated work pieces exit from the furnace onza pieces uniformly to forging temperature within downwardly inclined support I1. The flue gases the shortest possible time, thus with a minimum exit from the furnace through front and rear scale- This application is a continuation inpart vertical iiues I8 and Ill ofapplication Serial No. 35,922 filed June 29, 0 The innerA lining 20 of thetunnel IIl is `com- 1948, and now abandoned, and is directed more prsed of fused bubble alumina which is a high particularly to meansfor preventing local overl temperature refractory having heat insulating heating of the work and means for supporting properties.' A layer of heat insulating material the work in the furnace. For a consideration 1 2l lwill ordinarily be interposed between said `1inof whatI consider to be-novel and my invention, i ing and the steel casing 22 of the tunnel I0; attention is directed to the following portion of Full aerated fuel, preferably gaseous, is employed the specification and the drawings and ccncludto heat theexposed surface of said lining to eleing claim thereof. vated temperature, the lining having aplurality In the accompanying drawings, forming Vpart n of tangential fuel inlet ports 23 for this purof this specification, "0 pose so thatv the fuel will wash said surface and Fig. l is a longitudinal verticalsection of a bum in CODaG therewithfurnace embodying the present invention, The means for delivering the aerated fuel un- Fig. 2 is a transverse sectional view of the'imdel' Dressur@ t0 the inlet DGIS 23 COmDrSeS for proved` furnace, each port'a refractory nozzle 125 which projects Fig. 3is atransverse sectional viewof the `Work 2') ai ShOt distance mt@ Sal-Cl DOI- A Supply pipe supporting means in. the furnacechamber 21 dellvers the aerated fuel under pressure to a Fig. 4 shows how exposed ends ofrthe Work holder '2e-fof the refractory 1102219 25. piece may be protected .from overheating.v The Several fuel Supply DIDeS 21 for the sev- Fig, A5 shows how .the Support and guide rails eral burners or fuel discharge nozzles 25 are con- Of Fig, 4 may be maintained in, alignment, o nected in sets to individual fuel supply manifolds Fig. 6 shows a modification of the support 31, thereby permitting ready control of the heat means of Fig. 5. input` to the furnace at longitudinal intervals or Fig, 7 Shows 9, water piping myout for the work zones by control of valves 40 individual to supply support means, of Figs, 2 and 3, pipes 4I which deliver to said manifolds.

Fig. 8 shows a water piping layout forthe work $5 .The WOI'K Supporting means, 0I Skid rails I5 support means of Fig. v5. are supported at longitudinal intervals atop Fig 9 Shows a waterl piping myout for the transversely extending Walls 36 which also serve Work support, means of Fig- 6, to prevent draft through the `lower portion of The furnace comprises a refractorylined tunthe furnace and adllOnally Serve t0 divide the nel forming a cylindrical chamber In which will 4o lower portion of the heating Chamber into longiordinarily be supported on horizontally disposed udmal zones which are useful for heat control rails I3 atop supporting pillars I4, the tunnel 13111110598. having lateral arms I2 which rest on said rails. Where WOIk pieces are adapted to be pushed The tunnel is anchored at one` end to the suplfhIOUgll the furnace in @Dd t0 Grid relation; aS porting frame of which Jthe pillars I4 form a 45 the Square Section pieces W nFss. 2 and 3, the part, the balance of the tunnel being free to supporting meansA I5 therefor comprises a pair move on said rails as its length increases due to of' laterally spaced internally cooled rails I2 thermal expansion. which together form a cradle wherein the work The work pieces to be heated are passed pieces W are supported. These rails are interthrough the furnace chamber at a level which 50 connected-at longitudinal intervals by tubular is substantially within the central portion of the connecting members 43 so that cooling water in heating chamber. The means for supporting the rails 42 will also maintain the tubular conthework at such level comprises internally cooled necting members 43 relatively cool. Where the supportsA generally indicated at I5, the water members I3 are short and .tubular it is not necessupply-pipe being indica-ted` at 45` and the water 55 sary' to provide for a positive directional new of cooling water therethrough. It is sufficient to provide continuous flow through each of the rails 42 whereby any steam formed in the members 43 will rise to the cool stream in the rails 42, condense, and cool water will then run downward into the members 43. In practice, the thermal gradients in the members 43 have provided a natural circulation sufficient to avoid steam formation, due in part to the short members 43 required. When positive unidirectional flow through the members 43 is not provided it is preferred to recirculate water through the rails in a closed system to prevent accumulations of deposits such as lime in the rails and members. Where the problemV of cooling the members 43 becomes greater then suitable orifices may be installed in the lines as shown in Fig.'7, Where valves 50 and 5| are installed loutside the furnace heating chamber l for water flow control, one valve 50 at a rail inlet to the furnace and the other valve I at the paired rail outlet from the furnace. This provides by now restrictions a positive continuous directional flow from the unrestricted rail inlet 52 through the members 43 to the unrestricted rail outlet 53, as shown by directional arrows adjacent mem# bers 43.

It will be appreciated that where square sectional pieces W are pushed end to end along pairs of rails as shown in Figs. 2 and 3 there is Y the rails to spread them. The connecting members 43 effectively maintain alignment of pairs of rails without additional water cooled tubes being supplied to the furnace.

In a furnace having a circular combustion chamber which is tangentially fired as illustrated in Fig. 2 it is possible to maintain combustion against the refractory Wall of the furnace as a relatively thin sleeve in the chamber and maintain unusually high wall temperatures for rapid high heat head heating. The central part of the chamber within the dashed line circle 54 is filled with products of combustion finding their way towards the end ues. These products of combustion are relatively inactive gases as compared to the reacting gases in the gas ame of the outer sleeve, hence the scale formation is held to a minimum during the fast heating of the work. The temperatures maintained in the heating chamber, generally in excess of 2600 F., are so high as to practically preclude the use of other than water cooled work supports, and the method of firing demands that the water cooled supports be kept out of in the furnace chamber, otherwise they would chill the gases before combustion was complete, and would absorb heat by convection as well as radiation removing as much as 40% more heat from the furnace. In a furnace having an inside chamber diameter of about inches the sleeve of burning gases may be considered as about 4 thick, and if the rails are kept 4 or more from the refractory walls they do not seriously affect the heating efficiency of the furnace. When the furnace has an inside chamber diameter of about inches, the burning gas sleeve has a thickness of about 6 inches.

Where the work pieces are required to be pushed through the furnace broadside first (as the work pieces W'P in Figs. 4, 5 and 6) the ends of said pieces tend to become overheated. This is due to a radiation phenomenon where the furnace wall temperature is considerably in excess the sleeve of burning gases of the final desired Work temperature. To prevent this overheating the pathway I5 along which the work pieces move through the furnace comprises, in addition to the internally cooled work supporting skid rails 4l (Figs. 4, 5 and 6), a pair of internally cooled side rails 48 which form a channel between which the work pieces are moved. Each side rail 48 is located with respect to the moving work so as to shield it from the excessive end heating effect of the entire side of the furnace wall, hence the end of the work piece is said to move in the shadow of the side rail. For this reason the side rails 48 are called shadow rails.

In rapid heating furnaces of this type billets may be heated to forging temperature with not over 0.002 inch of scale whereas conventional forge furnaces would allow to form at least .010 inch of scale, usually more. The improved forging die life possible with the materially reduced scale has been remarkable, usually of the order of 2 to 4 times the life formerly obtained. Where the shadow rails are not used the non-uniform heating of the ends overheats the steel and at the same time melts the thin scale thereon, making a sticky scale which rapidly deteriorates the forging dies. It has been demonstrated that to take full advantage of the rapid heating possible where a high heat head furnace is used, if billets are pushed broadside through the furnace, it is necessary to prevent overheating of the billet ends. The disclosed shadow rails serve this purpose admirably well.

In any refractory lined furnace for heating work to forging temperature there is a distinct advantage in using shadow rails when heating work with a high heat head in a manner tending to heat one portion of the Work faster than another. When operating with a heat head (the difference between furnace temperature and final desired work temperature) of to 400'F. or more, especially where the furnace temperature is over the scale melting temperature of 2440" F., if the work heats at the ends or at light sections faster than at other portions, then the faster heating portions may easily reach 2440 F. at their surface and form a plastic scale before the remainder of the piece reaches forging temperature. This plastic scale is worked into the surface of the piece in the dies and is very detrimental to the dies, causing materially shortened die life and subsequent machining troubles. Where shadow rails and support rails are both used, each side pair of shadow and support rails may be interconnected with water cooled tubular sections 55 as shown in Fig. 5, and the ow therethrough may be controlled by valves 56 and 51 as shown in Fig. 8. The support rails may also be joined by similar tubular sections 58 making the support rails and the shadow rails into a single structure as shown in Fig. 6. The controlled directional flow may be maintained quite easily by restricting flow in alternate rails at the inlet ends thereof, and at the outlet ends of intermediate rails as illustrated by valves 55 and 51 in Fig. 9.

It is believed to be apparent from the foregoing that the present invention provides for improvements in skid rail structure for a fast heating furnace which is Well adapted for its intended purpose.

Having thus described my invention, I claim:

Skid rail structure for supporting work pieces in a, furnace comprising a plurality of substan-` tially parallel internally cooled skid rails for conveying work pieces end to end through the furnace, cross pieces interconnecting said rails at- JOHN D. NESBITT.

6 References Cited in the ille of this patent UNITED STATES PATENTS OTHER REFERENCES Pages 338 and 339 naces, vol, II, second e lished by John Wiley of Trinks Industrial Furditon, copyright 1942, puband Sons, New York, N. Y. 

